Ichthyosis describes a group of genetically determined human diseases involving the epidermis; they are model diseases for understanding more common epidermal diseases such as psoriasis. In one form of ichthyosis, the harlequin fetus, there is a molecular abnormality in the conformation of the major epidermal structural proteins. The keratins in that disease have a cross-beta pleated sheet conformation rather than an alpha-helical conformation. Epidermal structural proteins will be isolated from different types of ichthyosis, and fractionated and then characterized with respect to amino acid analysis, electrophoretic mobility, molecular weight, N-terminal amino acids, peptide maps, covalent cross-links, and post-translational modifications, conformation and conformational stability. The antigenic identity or lack of identity between the various proteins and the ratio of the various structural proteins in normal and abnormal epidermis will also be determined. Transglutaminases and their substrates in the epidermis are studied. The enzymatic formation of disulfide bonds in keratinized structures is studied.